CYCLE INHIBITOR FOR AN ELECTRICAL TYPEWRITER
United States Patent 3643773
A typewriter baseplate with means for generating and transmitting electrical signals indicative of print and function cycles of the typewriter and having means for initiating typewriter operation in response to signals from a remote typewriter or computer is provided with mechanism for limiting the maximum cycle repetition rate of the typewriter to adapt to systems having slower signal processing rates. The cycling inhibit mechanism may serve other purposes such as preventing overloading of a buffer storage in the signal circuit and delaying cycling in response to uninterrupted input signals, during the carriage return periods.
US Patent References:
Justifying typewriter
Root - October 1949 - 2484649
Keyboard composed of three interrelated but individually replaceable units
Wentzel - January 1965 - 3165190
Transmitter receiver machine employing print sphere typewriter structure
Flieg - February 1966 - 3233715
Writing system generating code that differentiates between printing and functional operations
Becking et al. - April 1968 - 3380569
Signal responsive and signal generating means for single element print head typewriter
Knudsen et al. - December 1968 - 3414103
Justifying typewriter
Root - October 1949 - 2484649
Keyboard composed of three interrelated but individually replaceable units
Wentzel - January 1965 - 3165190
Transmitter receiver machine employing print sphere typewriter structure
Flieg - February 1966 - 3233715
Writing system generating code that differentiates between printing and functional operations
Becking et al. - April 1968 - 3380569
Signal responsive and signal generating means for single element print head typewriter
Knudsen et al. - December 1968 - 3414103
Application Number:
04/833647
Publication Date:
02/22/1972
Filing Date:
06/16/1969
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
400/367, D18/1, 400/377, 400/50
International Classes:
B41J3/42; B41J23/02; B41J5/30
Field of Search:
197/16,19,20,107-112
US Patent References:
| 3452851 | TYPEWRITER BASEPLATE ENABLING MACHINE OPERATION BY AND GENERATION OF ELECTRICAL SIGNAL | July 1969 | Holmes |
Primary Examiner:
Pulfrey, Robert E.
Assistant Examiner:
Pellegrino, Stephen C.
Claims:
What is claimed is
1. In combination with a typewriter having print mechanism driven through a print cycle clutch and means for engaging said clutch for a limited period in response to depression of any of a plurality of print keys of said typewriter whereby said typewriter cycles to perform the print operation associated with a depressed one of said keys, said typewriter having a clutch-controlling linkage which shifts in response to depression of any of said keys to initiate said engagement of said clutch, a cycle inhibitor mounted in said typewriter comprising a movable element positioned adjacent said clutch-controlling linkage and having a first position at which said linkage is free to shift to initiate engagement of said clutch and having a second position at which said movable element blocks said shifting of said clutch-controlling linkage, an electromechanical means associated with said movable element for shifting said movable element between said positions thereof.
2. The combination defined in claim 1 wherein said typewriter has function operation mechanism driven through a function cycle clutch and means for engaging said function cycle clutch for a limited period in response to depression of any of a plurality of function keys of said typewriter whereby said typewriter cycles to perform the function operation associated with a depressed one of said function keys and has an additional clutch-controlling linkage which shifts in response to depression of any of said function keys to initiate said engagement of said function clutch and has an additional element adjacent said additional clutch-controlling linkage movable to block said shifting thereof.
3. The combination defined in claim 1 wherein said typewriter has a baseplate attachment with a plurality of switches mounted thereon having actuator arms which extend up into said typewriter to sense, print and function operations thereof and having circuit means coupled to said switches for generating electrical signals indicative of said operations, wherein said movable element is an arm mounted on said baseplate and extending up into said typewriter to said clutch-engaging linkage and wherein said electromechanical means for shifting said movable element between said positions thereof is a solenoid mounted on said baseplate and having an armature coupled to said arm.
4. The combination defined in claim 1 wherein said typewriter has a switch producing a cycling signal at each cycle of said typewriter, further comprising circuit means connected between said cycling signal switch and said means for shifting said movable element for actuating said movable element shifting means to shift said movable element to said second position thereof for a predetermined interval after each cycling signal.
5. The combination defined in claim 1 wherein said typewriter has means for generating electrical signals indicative of typewriter operations and means for transmitting said signals to a location remote from the typewriter and has a buffer storage connected between said signal-generating means and said transmitting means for temporarily storing said signals for transmission at a rate which is slower than the rate at which said typewriter may generate said signals, wherein said means for shifting said movable element between said positions thereof has a control switch connected to said buffer storage and operated thereby to shift said movable element to said second position thereof in response to filling of said buffer storage.
6. The combination defined in claim 1 wherein said typewriter has means for receiving electrical signals from a remote source and means for operating elements of said typewriter in response to said signals and has a buffer storage connected between said receiving means and said operating means for temporarily storing signals received during the carriage return period of said typewriter for release thereto in the intervals between said carriage return periods, wherein said means for shifting said movable element between said positions thereof has a control switch connected to said buffer storage and operated thereby to hold said movable element at said second position thereof during said carriage return periods.
7. In a baseplate attachable to a typewriter to adapt said typewriter for transmitting groups of electrical signals indicative of print and function operations at the typewriter, said typewriter having a print cycle clutch and a function cycle clutch which are engaged by depression of print keys and function keys respectively to transmit drive to the print and function means respectively of the typewriter, the further combination comprising:
8. The combination defined in claim 7 further comprising an electrical power supply and circuit means coupled between said power supply and each of said solenoids for actuating said solenoids to shift said each of said armatures to said first positions thereof for a predetermined interval following transmission of a group of said signals.
1. In combination with a typewriter having print mechanism driven through a print cycle clutch and means for engaging said clutch for a limited period in response to depression of any of a plurality of print keys of said typewriter whereby said typewriter cycles to perform the print operation associated with a depressed one of said keys, said typewriter having a clutch-controlling linkage which shifts in response to depression of any of said keys to initiate said engagement of said clutch, a cycle inhibitor mounted in said typewriter comprising a movable element positioned adjacent said clutch-controlling linkage and having a first position at which said linkage is free to shift to initiate engagement of said clutch and having a second position at which said movable element blocks said shifting of said clutch-controlling linkage, an electromechanical means associated with said movable element for shifting said movable element between said positions thereof.
2. The combination defined in claim 1 wherein said typewriter has function operation mechanism driven through a function cycle clutch and means for engaging said function cycle clutch for a limited period in response to depression of any of a plurality of function keys of said typewriter whereby said typewriter cycles to perform the function operation associated with a depressed one of said function keys and has an additional clutch-controlling linkage which shifts in response to depression of any of said function keys to initiate said engagement of said function clutch and has an additional element adjacent said additional clutch-controlling linkage movable to block said shifting thereof.
3. The combination defined in claim 1 wherein said typewriter has a baseplate attachment with a plurality of switches mounted thereon having actuator arms which extend up into said typewriter to sense, print and function operations thereof and having circuit means coupled to said switches for generating electrical signals indicative of said operations, wherein said movable element is an arm mounted on said baseplate and extending up into said typewriter to said clutch-engaging linkage and wherein said electromechanical means for shifting said movable element between said positions thereof is a solenoid mounted on said baseplate and having an armature coupled to said arm.
4. The combination defined in claim 1 wherein said typewriter has a switch producing a cycling signal at each cycle of said typewriter, further comprising circuit means connected between said cycling signal switch and said means for shifting said movable element for actuating said movable element shifting means to shift said movable element to said second position thereof for a predetermined interval after each cycling signal.
5. The combination defined in claim 1 wherein said typewriter has means for generating electrical signals indicative of typewriter operations and means for transmitting said signals to a location remote from the typewriter and has a buffer storage connected between said signal-generating means and said transmitting means for temporarily storing said signals for transmission at a rate which is slower than the rate at which said typewriter may generate said signals, wherein said means for shifting said movable element between said positions thereof has a control switch connected to said buffer storage and operated thereby to shift said movable element to said second position thereof in response to filling of said buffer storage.
6. The combination defined in claim 1 wherein said typewriter has means for receiving electrical signals from a remote source and means for operating elements of said typewriter in response to said signals and has a buffer storage connected between said receiving means and said operating means for temporarily storing signals received during the carriage return period of said typewriter for release thereto in the intervals between said carriage return periods, wherein said means for shifting said movable element between said positions thereof has a control switch connected to said buffer storage and operated thereby to hold said movable element at said second position thereof during said carriage return periods.
7. In a baseplate attachable to a typewriter to adapt said typewriter for transmitting groups of electrical signals indicative of print and function operations at the typewriter, said typewriter having a print cycle clutch and a function cycle clutch which are engaged by depression of print keys and function keys respectively to transmit drive to the print and function means respectively of the typewriter, the further combination comprising:
8. The combination defined in claim 7 further comprising an electrical power supply and circuit means coupled between said power supply and each of said solenoids for actuating said solenoids to shift said each of said armatures to said first positions thereof for a predetermined interval following transmission of a group of said signals.
Description:
CROSS-REFERENCES TO RELATED APPLICATIONS
1. Allowed U.S. application Ser. No. 475,728 of Lawrence Holmes, Jr. filed July 29, 1965 for Communication System, now U.S. Pat. No. 3,453,379.
2. Allowed U.S. application Ser. No. 587,874 of Lawrence Holmes, Jr. filed Oct. 19, 1966 for Typewriter Baseplate, now U.S. Pat. No. 3,452,851.
BACKGROUND OF THE INVENTION
This invention relates to electronic data transmitting systems and more particularly to means for adapting office typewriters for use as data input or output terminals or for both purposes.
Computer systems as well as teletype communication networks frequently make use of a typewriterlike instrument as an input or output means and usually such instruments serve both purposes. These instruments have heretofore been highly specialized typewriters of expensive and intricate construction and have generally required a specially trained operator. However, the above-identified copending applications describe a recently developed means for adapting a common form of office typewriter for service as a data terminal with minimized expense and difficulty and without interfering with use of the typewriter for ordinary typing if it is desired.
Copending application Ser. No. 475,728 discloses circuits for this purpose while copending application Ser. No. 587,874 discloses an arrangement of the components which interact with the typewriter on a simple baseplate which can be emplaced on the existing typewriter very quickly and without requiring any difficult interconnection of elements of the baseplate with those of the typewriter. This enables the typewriter to be linked, by telephone lines or the like, with a remote typewriter or a computer.
In using ordinary typewriters for this purpose, a problem may be encountered with respect to differences in the maximum cycling repetition rate of such a typewriter and that of the system to which it is linked. The typewriter, for example, may be capable of transmitting signals at a greater rate than such signals can be processed by the transmission means or a computer or printer to which the typewriter is linked. The widely used American Standard Code for Information Interchange (ASCII) system, for example, is standardized to accommodate to a maximum signal rate of 10 characters per second whereas one form of commercial typewriter with which the system of the copending applications is adapted is capable of operation at 15.4 characters per second. In practice, the actual signal transmitting rate of such a typewriter may vary according to variations in the operator's manipulations at the keyboard and may reach the maximum value of 15.4 characters per second, if, for example, the operator strikes two keys simultaneously. Such transmission of signals at a rate greater than the standardized value may interfere with proper functioning of the system.
Similarly, difficulties may be encountered when an office typewriter is adapted to serve as a printout device. Some existing data transmitting systems deliver signals continuously whereas the typewriter periodically requires a pause for carriage return.
Thus, to adapt a commercial office typewriter of the kind under discussion to certain forms of data processing systems, which were designed for highly specialized terminal equipment, provisions may be needed for automatically fixing the minimum possible interval between successive cycles of the typewriter.
SUMMARY OF THE INVENTION
This invention provides means for inhibiting cycling of a data terminal typewriter to make the cycling repetition rate of the typewriter compatible with that of equipment to which the typewriter is linked.
Electrical typewriters of the type to which the invention is applicable have one or more clutches which engage in response to depression of a key to transmit torque from a continuously operating motor to the typewriter print or function mechanism controlled by the key. This invention provides inhibitor mechanism for preventing engagement of the clutch for a limited period following a previous cycle when it is necessary to avoid the problems discussed above.
Accordingly, it is an object of this invention to provide means for adapting an office typewriter to function as a data terminal with systems which may process signals at different repetition rates.
It is another object of the invention to provide means for limiting signal release rate of a transmitting typewriter to avoid overrunning an associated system which processes such signals at a lower rate.
It is still another object of the invention to provide for operation of a typewriter from input signals which may be received without interruption during carriage return periods.
The invention, together with other objects and advantages thereof, will best be understood by reference to the following description of a preferred embodiment in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a perspective view of a typewriter having baseplate means enabling the transmission of signals indicative of typewriter operations and providing for operation of the typewriter in response to incoming signals;
FIG. 2 is a view of a portion of the internal mechanism of the typewriter and baseplate of FIG. 1 including the print cycle clutch thereof and mechanism for inhibiting the cycle clutch operation when necessary;
FIG. 3 is a view of another portion of the internal mechanism of the typewriter and baseplate of FIG. 1 including the function operation clutch and means for inhibiting cycling thereof;
FIG. 4 is a schematic diagram illustrating one mode of controlling the clutch inhibit mechanism of FIGS. 2 and 3 to avoid the transmitting of signals at a rate exceeding the capability of external circuitry to which the typewriter may be linked, and
FIG. 5 diagrammatically illustrates another mode of control of the clutch inhibit mechanism in a system having a buffer storage for signals.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawing and initially to FIG. 1 thereof, there is shown a typewriter 11 of the type manufactured by the IBM Corporation and sold under the trademark "Selectric." This is a common form of office typewriter and differs from others in that the paper is stationary for each line of typing while the imprinting of characters on the paper is effected with a spherical printing head 12 which has all characters thereon and which is pivoted against the ribbon and paper to print a selected character after having been rotated and tilted to locate the character for printing. The printing head 12 is situated on a carrier 13 which moves relative to the paper a distance equivalent to one character space for each printing operation. Operation of printing head 12 and carrier 13 in this manner is initiated by depression of any of the typewriter print keys 14. The detailed structure and mode of operation of a typewriter 11 of this general type is well known to the art and is described, for example, in the above-identified copending applications. Accordingly, the detailed structure of the typewriter 11 will not be described herein except insofar as is necessary to understand the application of the present invention thereto.
To convert an office typewriter 11 of this kind to function as a data terminal whereby the typewriter may be linked with a remote typewriter, computer or the like, as an input and output instrument, a baseplate 16 is disposed at the underside of the typewriter. To generate electrical signals indicative of print and function operations at the typewriter 11, baseplate 16 carries a series of electrical switches 17 having actuator arms 18 which extend up into the typewriter mechanism to sense movement of certain linkages therein which shift in response to depression of the keys 14 in a pattern which is unique for each different key. Thus, the collective condition of switches 17 at each cycle identifies the particular operation being performed at that time. Baseplate 16 also carries a series of electrically actuated solenoids 19 having arms 21 extending upwardly into the typewriter mechanism to initiate operation of the typewriter in response to received signals. A multiconductor cable 22 connects each of the switches 17 and solenoids 19 with a logic circuit housing 23, having operator's control switches 24 at one surface thereof. Housing 23 contains circuitry for transmitting signals indicative of the condition of switches 17, following depression of any of the typewriter keys 14, to an output line 26 which may be connected with a remote typewriter, printer or computer via telephone lines or other transmission means. Housing 23 also contains circuitry for energizing the several baseplate solenoids 19 in response to signals received over line 26 to initiate operations at typewriter 11 which are indicated by such received signals. Suitable circuitry for both the input and output functions of the typewriter 11 is described in detail in the above-identified copending applications and accordingly will not be described in detail herein.
As discussed above, the interval between successive cycles of the typewriter 11 may, under certain conditions, be so brief that output signals are generated at a rate greater than can be transmitted to the output line 26 without interfering with operation of slower systems which are coupled to the typewriter. Conversely, at certain times, signals may be received over line 26 at a time when the typewriter 11 is temporarily unable to print in response to such signals. Accordingly, the present invention provides mechanism which responds to electrical control signals to limit the rate at which the typewriter can be operated to release successive signals and to delay operation, when necessary, in response to received signals.
The typewriter 11 may perform two different categories of operations each of which involves different drive mechanisms. These two types of operation consist of print operations which result in printing of a character by the printing head 12 and function operations, such as space, backspace, index, etc., which do not require operation of the printing head. Accordingly, two cycle inhibitor mechanisms are needed including a print cycle inhibitor 27 and a function inhibitor mechanism 28.
Considering first the print cycle inhibitor 27, with reference to FIG. 2, the previously described printing head is pivoted to imprint a character by turning of a cycle shaft 29 through 180° of rotation. The cycle shaft 29 is turned in this manner in response to depression of any of the print keys 14 in that depression of the key causes the temporary engagement of a cycle clutch 31 coupled between the cycle shaft 29 and the typewriter drive motor 30. As set forth in greater detail in the above identified copending applications, each print key 14 is carried on a pivotable key lever 32 which is urged upwardly by spring means 33. Below the key lever 32 is an interposer 34 having an upwardly extending finger 37 positioned to be contacted by a pawl 38 of the associated key lever 32 whereby the interposer is urged downwardly by depression of the key 14. Downward movement of the interposer 34 in turn depresses a cycle bail 39 which then depresses a cycle clutch latch pawl 41 whereby it is able to slide under a cycle clutch keeper 42. Pawl 41 is carried on a cycle clutch latch link 43 which is urged toward the front end 45 of the typewriter by a spring 44 but which is normally prevented from moving in that direction under the action of the spring by abutment of the pawl 41 against keeper 42 until such time as the pawl is depressed as discussed above. With the pawl 41 disengaged from keeper 42, link 43 moves forwardly through the action of spring 44 and thereby withdraws a cycle clutch latch 46 from a cycle clutch sleeve 47. Cycle clutch latch 46 normally abuts a step 48 on sleeve 47 to keep the cycle clutch 31 from engaging. Upon withdrawal of the latch 46 as a result of depression of a print key 14, the clutch engages to turn cycle shaft 29. After 180° of angular motion of the cycle shaft 29, during which character imprinting occurs, a second step 48' on sleeve 47 contacts the cycle clutch latch 46 to disengage the clutch and end the print cycle. The cycle clutch latch 46 is restored to its rearward position for this purpose by rotation of a filter shaft 49 which is turned by the cycle clutch shaft and which has cam projections operating a pivoting cycle clutch latch restoring arm 51.
To prevent a print cycle from occurring too rapidly after a previous cycle, the present invention provides means for temporarily blocking operation of one of the above-described elements which must move in order to allow engagement of the cycle clutch 31. In particular, the cycle clutch inhibitor 27 in this example acts to block the forward movement of the cycle clutch latch 46 when it is desired to delay a cycle relative to the previous one.
The typewriter 11 in this embodiment of the invention is provided with the baseplate 16 in accordance with copending application Ser. No. 587,874 which carries the solenoids 19 with upwardly extending arms 21, switches 17 and other mechanisms necessary to adapt the typewriter for transmitting print and function operation signals and for operating in response thereto. In keeping with this concept, the clutch inhibitor mechanism 27 is preferably mounted on baseplate 16 and preferably operates without requiring a positive fastening to internal elements of the typewriter. Accordingly, the inhibitor 27 may be comprised of an electrically operated solenoid 52 having an armature shaft 53 which retracts towards the body of the solenoid in response to energization thereof. Shaft 53 is urged outwardly from the solenoid body by a spring 54 acting against a flange 55 on the shaft. An arm 56 is pivoted to fingers 57 extending from the solenoid 52 and has a lower end with a slot 58 through which a pin 59 is transpierced to engage the lower end of the arm with the end of armature shaft 53 whereby retraction of the armature shaft pivots the upper end of arm 56 towards the rear of the typewriter. Arm 56 extends upwardly through an opening 61 in the baseplate 16 to a position where the upper end of the arm is situated a small distance forwardly from the lower end of the cycle clutch latch 46 when the solenoid 52 is unenergized and the cycle clutch latch is at its rearward position. In some commercial typewriters, the arm 56 may need to be angled, in a direction normal to the plane of movement of the arm, in order to reach this position due to the presence of other mechanism.
Thus, with the solenoid 52 energized, arm 56 does not interfere with operation of the cycle clutch latch 46 as described above. Upon being energized by a control signal, solenoid 52 pivots the upper end of arm 56 forward to abut the cycle clutch latch 46 whereby it cannot retract from sleeve 47. Thus, under this condition, a print cycle will not occur until such time as the solenoid 52 is subsequently deenergized.
As pointed out above, it is generally necessary to inhibit function operations of the typewriter simultaneously with the inhibition of the print cycle mechanism. Referring now to FIG. 3, the function operations of interest are powered by 180° rotation of an operational shaft 62 as a result of temporary engagement of a function clutch mechanism 63 in response depression of a function key such as the backspace key 14' shown in FIG. 3. Depression of key 14' pivots an associated key lever 64 against the upwardly biasing action of a spring 66 and a key lever pawl 67 is thereby caused to depress the forward end of an interposer 68. Interposer 68 is urged toward the rear of the typewriter by a spring 69 but is normally prevented from moving rearwardly in that a latch 71 carried on the interposer engages a bracket 72. Depression of the forward end of interposer 68 releases latch 71 from bracket 72 enabling the spring 69 to draw the interposer rearwardly. Rearward movement of interposer 68 acts through linkage 73 to pivot a clutch release arm 74 and lever 74' downwardly. The clutch release arm 74, in its upward position, contacts a latching surface 76 on clutch wheel 77 to block rotation of the clutch wheel thereby holding the function clutch 63 disengaged.
Upon downward movement of the forward end of clutch release arm 74 as a result of depression of a function key such as key 14', clutch wheel 77 is released and the clutch engages to turn operational shaft 62. After 180° of rotation, a second latch surface 76' on the clutch wheel contacts the forward end of the clutch release arm 74 and the clutch 63 again disengages in preparation for a subsequent function cycle.
Accordingly, the function cycle at the typewriter may be delayed as necessary by temporarily preventing the downward movement of the forward end of clutch release arm 74. This is effected by the function clutch inhibitor mechanism 28.
Inhibitor mechanism 28 includes a solenoid 78 mounted on the underside of baseplate 16 beneath the clutch release arm 74 and having an armature shaft 79 which is retracted by energization of the solenoid. Armature shaft 79 is normally held at its unretracted position by a compression spring 81 bearing against a flange 82 on the shaft. An arm 83 has a central portion pivoted to fingers 84 extending from solenoid 78 above shaft 79, the lower end of the arm having a slot 86 to receive a pin 87 transpierced through the end of armature shaft 79 whereby retraction of the armature shaft pivots the upper end of arm 83 forwardly. Arm 83 extends upwardly through an opening 88 in baseplate 16 to a position at which the extreme upper end of the arm is moved under the clutch release arm lever 74' when the solenoid 78 is energized, the top of the arm being situated slightly to the rear of the lever 74' when the solenoid is unenergized. Accordingly, energizing of the function cycle inhibitor solenoid 78 shifts arm 83 to block downward pivoting of the clutch release arm 74. This in turn blocks engagement of the function cycle clutch 63, when a function key such as key 14' is depressed, until such time as the solenoid 78 is deenergized.
Thus, with reference to both FIG. 2 and FIG. 3, energizing of the two inhibit solenoids 52 and 78 provides means by which cycling at the typewriter 11 in either its transmitting or receiving function may be delayed relative to the previous cycle to the extent necessary to accommodate to the signal processing characteristics of the system to which the typewriter is coupled. As different ones of such systems may present different problems in this respect, the circuitry for controlling the operations of the solenoids 52 and 78 may take several forms.
FIG. 4, for example, diagrammatically illustrates circuit means through which the transmit logic of the typewriter 11 controls the solenoids to avoid the transmitting of signals to line 26 at a repetition rate greater than can be accommodated by a slower remote system to which the typewriter may be linked. The transmit logic can be represented as comprised of a circuit 89 having seven input channels each coupled to an associated individual one of the baseplate switches 17 and which generates signal bits indicative of the condition of the associated switch when a cycling sensing switch 17' on the baseplate closes indicating that the typewriter is commencing a print or function operation. Switch 17' starts a clock pulse source 91 which in turn activates circuit 89 and a parallel to serial signal converter 92 which sequentially reads off the mark or space signal bit in each of the seven channels to the output line 28. The detailed circuit for this purpose is described at length in copending application Ser. No. 475,728.
To avoid too rapid transmission of one set of signals after the proceeding set, such as could occur if two keys of the typewriter are depressed simultaneously or near simultaneously, the two inhibitors solenoids 52 and 78 are parallel connected with a power supply 93 through a solid-state switch 94. Switch 94 is normally nonconducting and, under this condition, the solenoids are not energized and the inhibitor mechanism does not interfere with transmission of signals in response to operation of the typewriter keys. However, a bit counter 96 is coupled to the clock 91 to count the bit in the signal accompanying each typewriter operation. When the signal bits for each cycle have been counted, counter 96 immediately closes the switch 94 for a predetermined period corresponding to the minimum acceptable interval between successive signals which are being transmitted over line 28. Under most conditions, the operator does not depress keys at a rate greater than can be accommodated by most data processing systems. Thus, following a cycle, the inhibit mechanism is both actuated and deactuated before the next cycle commences. However, as discussed above, special conditions can occur at which the cycling repetition rate would be too rapid and it is under these conditions that the inhibit mechanism actually delays cycling.
Other modes of control of the inhibitor mechanism may be employed where appropriate, either separately or in conjunction with the control described above. As indicated diagrammatically in FIG. 5, a buffer storage 97 for the signal bits representative of several successive operations may be situated between the baseplate 16 circuits and the converter circuit 92' which serializes signals transmitted to the line 26 and converts incoming signals from serial to parallel form. Where the typewriter is being operated by signals from a remote source, received over line 26, buffer storage 97 may serve the purpose of storing those signals which are received while the typewriter is engaged in a carriage return. Buffer 97 subsequently releases the stored signals to the baseplate 16 after the carriage return has been completed. As the typewriter is capable of cycling faster than the rate at which signals are received over line 26, the typewriter catches up with the incoming signals before completion of typing of the line following each carriage return. Such a mode of operation may require that cycling of the typewriter be inhibited during the period that information is being accumulated in the buffer 97 and for this purpose the buffer controls a solid-state switch 94', connected between the power supply 93' and the two inhibitor solenoids 52 and 78, to energize the solenoids during the carriage return period.
During the transmit function of the typewriter, buffer 97 may serve to accumulate signals which are produced by operation of the typewriter at a rate greater than can be accommodated by the line 28 and associated equipment, the stored signals being transmitted during a subsequent period when the typewriter is operating at less than the maximum acceptable rate or during the carriage return period. While this will generally avoid problems from differences in signal processing rate, there is a possibility that the buffer 97 would become filled to capacity. Accordingly, under this condition, the buffer closes the solid-state switch 94' to block further cycling of the typewriter until the buffer is at least partially discharged. It will be apparent that still other modes of control of the inhibitor solenoids 52 and 78 may be advantageous in different systems where basically similar problems are encountered.
1. Allowed U.S. application Ser. No. 475,728 of Lawrence Holmes, Jr. filed July 29, 1965 for Communication System, now U.S. Pat. No. 3,453,379.
2. Allowed U.S. application Ser. No. 587,874 of Lawrence Holmes, Jr. filed Oct. 19, 1966 for Typewriter Baseplate, now U.S. Pat. No. 3,452,851.
BACKGROUND OF THE INVENTION
This invention relates to electronic data transmitting systems and more particularly to means for adapting office typewriters for use as data input or output terminals or for both purposes.
Computer systems as well as teletype communication networks frequently make use of a typewriterlike instrument as an input or output means and usually such instruments serve both purposes. These instruments have heretofore been highly specialized typewriters of expensive and intricate construction and have generally required a specially trained operator. However, the above-identified copending applications describe a recently developed means for adapting a common form of office typewriter for service as a data terminal with minimized expense and difficulty and without interfering with use of the typewriter for ordinary typing if it is desired.
Copending application Ser. No. 475,728 discloses circuits for this purpose while copending application Ser. No. 587,874 discloses an arrangement of the components which interact with the typewriter on a simple baseplate which can be emplaced on the existing typewriter very quickly and without requiring any difficult interconnection of elements of the baseplate with those of the typewriter. This enables the typewriter to be linked, by telephone lines or the like, with a remote typewriter or a computer.
In using ordinary typewriters for this purpose, a problem may be encountered with respect to differences in the maximum cycling repetition rate of such a typewriter and that of the system to which it is linked. The typewriter, for example, may be capable of transmitting signals at a greater rate than such signals can be processed by the transmission means or a computer or printer to which the typewriter is linked. The widely used American Standard Code for Information Interchange (ASCII) system, for example, is standardized to accommodate to a maximum signal rate of 10 characters per second whereas one form of commercial typewriter with which the system of the copending applications is adapted is capable of operation at 15.4 characters per second. In practice, the actual signal transmitting rate of such a typewriter may vary according to variations in the operator's manipulations at the keyboard and may reach the maximum value of 15.4 characters per second, if, for example, the operator strikes two keys simultaneously. Such transmission of signals at a rate greater than the standardized value may interfere with proper functioning of the system.
Similarly, difficulties may be encountered when an office typewriter is adapted to serve as a printout device. Some existing data transmitting systems deliver signals continuously whereas the typewriter periodically requires a pause for carriage return.
Thus, to adapt a commercial office typewriter of the kind under discussion to certain forms of data processing systems, which were designed for highly specialized terminal equipment, provisions may be needed for automatically fixing the minimum possible interval between successive cycles of the typewriter.
SUMMARY OF THE INVENTION
This invention provides means for inhibiting cycling of a data terminal typewriter to make the cycling repetition rate of the typewriter compatible with that of equipment to which the typewriter is linked.
Electrical typewriters of the type to which the invention is applicable have one or more clutches which engage in response to depression of a key to transmit torque from a continuously operating motor to the typewriter print or function mechanism controlled by the key. This invention provides inhibitor mechanism for preventing engagement of the clutch for a limited period following a previous cycle when it is necessary to avoid the problems discussed above.
Accordingly, it is an object of this invention to provide means for adapting an office typewriter to function as a data terminal with systems which may process signals at different repetition rates.
It is another object of the invention to provide means for limiting signal release rate of a transmitting typewriter to avoid overrunning an associated system which processes such signals at a lower rate.
It is still another object of the invention to provide for operation of a typewriter from input signals which may be received without interruption during carriage return periods.
The invention, together with other objects and advantages thereof, will best be understood by reference to the following description of a preferred embodiment in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a perspective view of a typewriter having baseplate means enabling the transmission of signals indicative of typewriter operations and providing for operation of the typewriter in response to incoming signals;
FIG. 2 is a view of a portion of the internal mechanism of the typewriter and baseplate of FIG. 1 including the print cycle clutch thereof and mechanism for inhibiting the cycle clutch operation when necessary;
FIG. 3 is a view of another portion of the internal mechanism of the typewriter and baseplate of FIG. 1 including the function operation clutch and means for inhibiting cycling thereof;
FIG. 4 is a schematic diagram illustrating one mode of controlling the clutch inhibit mechanism of FIGS. 2 and 3 to avoid the transmitting of signals at a rate exceeding the capability of external circuitry to which the typewriter may be linked, and
FIG. 5 diagrammatically illustrates another mode of control of the clutch inhibit mechanism in a system having a buffer storage for signals.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawing and initially to FIG. 1 thereof, there is shown a typewriter 11 of the type manufactured by the IBM Corporation and sold under the trademark "Selectric." This is a common form of office typewriter and differs from others in that the paper is stationary for each line of typing while the imprinting of characters on the paper is effected with a spherical printing head 12 which has all characters thereon and which is pivoted against the ribbon and paper to print a selected character after having been rotated and tilted to locate the character for printing. The printing head 12 is situated on a carrier 13 which moves relative to the paper a distance equivalent to one character space for each printing operation. Operation of printing head 12 and carrier 13 in this manner is initiated by depression of any of the typewriter print keys 14. The detailed structure and mode of operation of a typewriter 11 of this general type is well known to the art and is described, for example, in the above-identified copending applications. Accordingly, the detailed structure of the typewriter 11 will not be described herein except insofar as is necessary to understand the application of the present invention thereto.
To convert an office typewriter 11 of this kind to function as a data terminal whereby the typewriter may be linked with a remote typewriter, computer or the like, as an input and output instrument, a baseplate 16 is disposed at the underside of the typewriter. To generate electrical signals indicative of print and function operations at the typewriter 11, baseplate 16 carries a series of electrical switches 17 having actuator arms 18 which extend up into the typewriter mechanism to sense movement of certain linkages therein which shift in response to depression of the keys 14 in a pattern which is unique for each different key. Thus, the collective condition of switches 17 at each cycle identifies the particular operation being performed at that time. Baseplate 16 also carries a series of electrically actuated solenoids 19 having arms 21 extending upwardly into the typewriter mechanism to initiate operation of the typewriter in response to received signals. A multiconductor cable 22 connects each of the switches 17 and solenoids 19 with a logic circuit housing 23, having operator's control switches 24 at one surface thereof. Housing 23 contains circuitry for transmitting signals indicative of the condition of switches 17, following depression of any of the typewriter keys 14, to an output line 26 which may be connected with a remote typewriter, printer or computer via telephone lines or other transmission means. Housing 23 also contains circuitry for energizing the several baseplate solenoids 19 in response to signals received over line 26 to initiate operations at typewriter 11 which are indicated by such received signals. Suitable circuitry for both the input and output functions of the typewriter 11 is described in detail in the above-identified copending applications and accordingly will not be described in detail herein.
As discussed above, the interval between successive cycles of the typewriter 11 may, under certain conditions, be so brief that output signals are generated at a rate greater than can be transmitted to the output line 26 without interfering with operation of slower systems which are coupled to the typewriter. Conversely, at certain times, signals may be received over line 26 at a time when the typewriter 11 is temporarily unable to print in response to such signals. Accordingly, the present invention provides mechanism which responds to electrical control signals to limit the rate at which the typewriter can be operated to release successive signals and to delay operation, when necessary, in response to received signals.
The typewriter 11 may perform two different categories of operations each of which involves different drive mechanisms. These two types of operation consist of print operations which result in printing of a character by the printing head 12 and function operations, such as space, backspace, index, etc., which do not require operation of the printing head. Accordingly, two cycle inhibitor mechanisms are needed including a print cycle inhibitor 27 and a function inhibitor mechanism 28.
Considering first the print cycle inhibitor 27, with reference to FIG. 2, the previously described printing head is pivoted to imprint a character by turning of a cycle shaft 29 through 180° of rotation. The cycle shaft 29 is turned in this manner in response to depression of any of the print keys 14 in that depression of the key causes the temporary engagement of a cycle clutch 31 coupled between the cycle shaft 29 and the typewriter drive motor 30. As set forth in greater detail in the above identified copending applications, each print key 14 is carried on a pivotable key lever 32 which is urged upwardly by spring means 33. Below the key lever 32 is an interposer 34 having an upwardly extending finger 37 positioned to be contacted by a pawl 38 of the associated key lever 32 whereby the interposer is urged downwardly by depression of the key 14. Downward movement of the interposer 34 in turn depresses a cycle bail 39 which then depresses a cycle clutch latch pawl 41 whereby it is able to slide under a cycle clutch keeper 42. Pawl 41 is carried on a cycle clutch latch link 43 which is urged toward the front end 45 of the typewriter by a spring 44 but which is normally prevented from moving in that direction under the action of the spring by abutment of the pawl 41 against keeper 42 until such time as the pawl is depressed as discussed above. With the pawl 41 disengaged from keeper 42, link 43 moves forwardly through the action of spring 44 and thereby withdraws a cycle clutch latch 46 from a cycle clutch sleeve 47. Cycle clutch latch 46 normally abuts a step 48 on sleeve 47 to keep the cycle clutch 31 from engaging. Upon withdrawal of the latch 46 as a result of depression of a print key 14, the clutch engages to turn cycle shaft 29. After 180° of angular motion of the cycle shaft 29, during which character imprinting occurs, a second step 48' on sleeve 47 contacts the cycle clutch latch 46 to disengage the clutch and end the print cycle. The cycle clutch latch 46 is restored to its rearward position for this purpose by rotation of a filter shaft 49 which is turned by the cycle clutch shaft and which has cam projections operating a pivoting cycle clutch latch restoring arm 51.
To prevent a print cycle from occurring too rapidly after a previous cycle, the present invention provides means for temporarily blocking operation of one of the above-described elements which must move in order to allow engagement of the cycle clutch 31. In particular, the cycle clutch inhibitor 27 in this example acts to block the forward movement of the cycle clutch latch 46 when it is desired to delay a cycle relative to the previous one.
The typewriter 11 in this embodiment of the invention is provided with the baseplate 16 in accordance with copending application Ser. No. 587,874 which carries the solenoids 19 with upwardly extending arms 21, switches 17 and other mechanisms necessary to adapt the typewriter for transmitting print and function operation signals and for operating in response thereto. In keeping with this concept, the clutch inhibitor mechanism 27 is preferably mounted on baseplate 16 and preferably operates without requiring a positive fastening to internal elements of the typewriter. Accordingly, the inhibitor 27 may be comprised of an electrically operated solenoid 52 having an armature shaft 53 which retracts towards the body of the solenoid in response to energization thereof. Shaft 53 is urged outwardly from the solenoid body by a spring 54 acting against a flange 55 on the shaft. An arm 56 is pivoted to fingers 57 extending from the solenoid 52 and has a lower end with a slot 58 through which a pin 59 is transpierced to engage the lower end of the arm with the end of armature shaft 53 whereby retraction of the armature shaft pivots the upper end of arm 56 towards the rear of the typewriter. Arm 56 extends upwardly through an opening 61 in the baseplate 16 to a position where the upper end of the arm is situated a small distance forwardly from the lower end of the cycle clutch latch 46 when the solenoid 52 is unenergized and the cycle clutch latch is at its rearward position. In some commercial typewriters, the arm 56 may need to be angled, in a direction normal to the plane of movement of the arm, in order to reach this position due to the presence of other mechanism.
Thus, with the solenoid 52 energized, arm 56 does not interfere with operation of the cycle clutch latch 46 as described above. Upon being energized by a control signal, solenoid 52 pivots the upper end of arm 56 forward to abut the cycle clutch latch 46 whereby it cannot retract from sleeve 47. Thus, under this condition, a print cycle will not occur until such time as the solenoid 52 is subsequently deenergized.
As pointed out above, it is generally necessary to inhibit function operations of the typewriter simultaneously with the inhibition of the print cycle mechanism. Referring now to FIG. 3, the function operations of interest are powered by 180° rotation of an operational shaft 62 as a result of temporary engagement of a function clutch mechanism 63 in response depression of a function key such as the backspace key 14' shown in FIG. 3. Depression of key 14' pivots an associated key lever 64 against the upwardly biasing action of a spring 66 and a key lever pawl 67 is thereby caused to depress the forward end of an interposer 68. Interposer 68 is urged toward the rear of the typewriter by a spring 69 but is normally prevented from moving rearwardly in that a latch 71 carried on the interposer engages a bracket 72. Depression of the forward end of interposer 68 releases latch 71 from bracket 72 enabling the spring 69 to draw the interposer rearwardly. Rearward movement of interposer 68 acts through linkage 73 to pivot a clutch release arm 74 and lever 74' downwardly. The clutch release arm 74, in its upward position, contacts a latching surface 76 on clutch wheel 77 to block rotation of the clutch wheel thereby holding the function clutch 63 disengaged.
Upon downward movement of the forward end of clutch release arm 74 as a result of depression of a function key such as key 14', clutch wheel 77 is released and the clutch engages to turn operational shaft 62. After 180° of rotation, a second latch surface 76' on the clutch wheel contacts the forward end of the clutch release arm 74 and the clutch 63 again disengages in preparation for a subsequent function cycle.
Accordingly, the function cycle at the typewriter may be delayed as necessary by temporarily preventing the downward movement of the forward end of clutch release arm 74. This is effected by the function clutch inhibitor mechanism 28.
Inhibitor mechanism 28 includes a solenoid 78 mounted on the underside of baseplate 16 beneath the clutch release arm 74 and having an armature shaft 79 which is retracted by energization of the solenoid. Armature shaft 79 is normally held at its unretracted position by a compression spring 81 bearing against a flange 82 on the shaft. An arm 83 has a central portion pivoted to fingers 84 extending from solenoid 78 above shaft 79, the lower end of the arm having a slot 86 to receive a pin 87 transpierced through the end of armature shaft 79 whereby retraction of the armature shaft pivots the upper end of arm 83 forwardly. Arm 83 extends upwardly through an opening 88 in baseplate 16 to a position at which the extreme upper end of the arm is moved under the clutch release arm lever 74' when the solenoid 78 is energized, the top of the arm being situated slightly to the rear of the lever 74' when the solenoid is unenergized. Accordingly, energizing of the function cycle inhibitor solenoid 78 shifts arm 83 to block downward pivoting of the clutch release arm 74. This in turn blocks engagement of the function cycle clutch 63, when a function key such as key 14' is depressed, until such time as the solenoid 78 is deenergized.
Thus, with reference to both FIG. 2 and FIG. 3, energizing of the two inhibit solenoids 52 and 78 provides means by which cycling at the typewriter 11 in either its transmitting or receiving function may be delayed relative to the previous cycle to the extent necessary to accommodate to the signal processing characteristics of the system to which the typewriter is coupled. As different ones of such systems may present different problems in this respect, the circuitry for controlling the operations of the solenoids 52 and 78 may take several forms.
FIG. 4, for example, diagrammatically illustrates circuit means through which the transmit logic of the typewriter 11 controls the solenoids to avoid the transmitting of signals to line 26 at a repetition rate greater than can be accommodated by a slower remote system to which the typewriter may be linked. The transmit logic can be represented as comprised of a circuit 89 having seven input channels each coupled to an associated individual one of the baseplate switches 17 and which generates signal bits indicative of the condition of the associated switch when a cycling sensing switch 17' on the baseplate closes indicating that the typewriter is commencing a print or function operation. Switch 17' starts a clock pulse source 91 which in turn activates circuit 89 and a parallel to serial signal converter 92 which sequentially reads off the mark or space signal bit in each of the seven channels to the output line 28. The detailed circuit for this purpose is described at length in copending application Ser. No. 475,728.
To avoid too rapid transmission of one set of signals after the proceeding set, such as could occur if two keys of the typewriter are depressed simultaneously or near simultaneously, the two inhibitors solenoids 52 and 78 are parallel connected with a power supply 93 through a solid-state switch 94. Switch 94 is normally nonconducting and, under this condition, the solenoids are not energized and the inhibitor mechanism does not interfere with transmission of signals in response to operation of the typewriter keys. However, a bit counter 96 is coupled to the clock 91 to count the bit in the signal accompanying each typewriter operation. When the signal bits for each cycle have been counted, counter 96 immediately closes the switch 94 for a predetermined period corresponding to the minimum acceptable interval between successive signals which are being transmitted over line 28. Under most conditions, the operator does not depress keys at a rate greater than can be accommodated by most data processing systems. Thus, following a cycle, the inhibit mechanism is both actuated and deactuated before the next cycle commences. However, as discussed above, special conditions can occur at which the cycling repetition rate would be too rapid and it is under these conditions that the inhibit mechanism actually delays cycling.
Other modes of control of the inhibitor mechanism may be employed where appropriate, either separately or in conjunction with the control described above. As indicated diagrammatically in FIG. 5, a buffer storage 97 for the signal bits representative of several successive operations may be situated between the baseplate 16 circuits and the converter circuit 92' which serializes signals transmitted to the line 26 and converts incoming signals from serial to parallel form. Where the typewriter is being operated by signals from a remote source, received over line 26, buffer storage 97 may serve the purpose of storing those signals which are received while the typewriter is engaged in a carriage return. Buffer 97 subsequently releases the stored signals to the baseplate 16 after the carriage return has been completed. As the typewriter is capable of cycling faster than the rate at which signals are received over line 26, the typewriter catches up with the incoming signals before completion of typing of the line following each carriage return. Such a mode of operation may require that cycling of the typewriter be inhibited during the period that information is being accumulated in the buffer 97 and for this purpose the buffer controls a solid-state switch 94', connected between the power supply 93' and the two inhibitor solenoids 52 and 78, to energize the solenoids during the carriage return period.
During the transmit function of the typewriter, buffer 97 may serve to accumulate signals which are produced by operation of the typewriter at a rate greater than can be accommodated by the line 28 and associated equipment, the stored signals being transmitted during a subsequent period when the typewriter is operating at less than the maximum acceptable rate or during the carriage return period. While this will generally avoid problems from differences in signal processing rate, there is a possibility that the buffer 97 would become filled to capacity. Accordingly, under this condition, the buffer closes the solid-state switch 94' to block further cycling of the typewriter until the buffer is at least partially discharged. It will be apparent that still other modes of control of the inhibitor solenoids 52 and 78 may be advantageous in different systems where basically similar problems are encountered.